DOCSLIB.ORG

Phylum Porifera.Pdf

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Phylum Porifera.Pdf Phylum Porifera (Sponges) body consists of just 4 kinds of cells arranged ~9,000 living species; >2200 fossil forms around a system of pores and canals abundant fossil record though multicellular, no true organs or even tissues eg. first signs of multicellular life are in 750 MY old rock, in this same rock are unique chemical signatures of sponges sponges are closely related to the group of eg. newly discovered(2010) fossils that may be sponges have protozoan protists called the been found in 635-659 MY old rocks choanoflagellates whose cells very closely eg. 400 MY ago sponges dominated the oceans as reef builders resemble the collar cells of sponges eg. some fossil sponge reefs are much larger than the great th ~ 1/4 of their genes are shared by all other animals barrier reef à covered an arc across most of N Europe 200 MY ago about 1000 of those are absent from protozoa and other protists fossilized into hard rock used to build castles and other buildings in the Middle ages à may hold key to origin of multicellularity genetic analysis indicates that sponges are the most while multicellular their structure is unlike any other primitive animal group alive today animal group ancient spongelike ancestors were the first early biologists thought they were some kind of plant animals all are aquatic, mostly marine all other animal groups descended from this ancestor found at all depths from intertidal to the abyssal zone - the earliest sponges in symbiosis with bacteria may have significantly helped to aerate the ancient oceans making them more suitable for animal diversification a few (~150 sp./27 US) occur in freshwater sponges are some of the simplest animals most range from <1/2 inch to over 6 feet tall (=loggerhead sponges) all sponges are sessile Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 1 Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 2 some are round, flat, grow as crusts or vaselike but only of its own species (if 2 blended together) most are assymetrical sponges need only very small amts of oxygen and, as some of the some are radially symmetrical earliest animals, may have played a role in helping to raise earths oxygen levels by feeding on dead or dying bacteria that often brightly colored: yellows, reds, greens, would deoxygenate the water oranges, lavenders Body Plan à pigments in surface cells body is a network of pores, canals and passageways most are colonial – colonies formed by budding no “mouth” all are sessile (non motile) , most are filter feeders water is pumped through these passageways and the but larvae are free swimming (motile) animals filter nutrients from the water currents very simple in structure small openings are pores or ostia where water is drawn into the sponge though multicellular, they function largely like a colony of unicellular organisms water exits the sponge through larger openings = oscula (sing. = osculum) Aristotle thought they were an intermediate between plants and animals natural selection favored an increase in surface area cellular level or organization leading to more complex “folding” of the sponge: à no true tissues or organs; loose aggregate of cells simple to more elaborate canal systems à masses of cells in gelatinous matrix= mesophyll à only a few cells have specialized for a particular function a. asconoid (6 kinds of cells in sponges; simplest type humans have >250 kinds of cells) very small tube shaped sponges large central cavity = spongocoel eg. can force sponge through fine sieve to separate cells in via small openings called ostia and individual cells will reform a sponge out through single osculum Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 3 Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 4 functions b. syconoid derived from asconoid pattern by folding most cells are “totipotent” (ie. can change form more branching has incurrent canals and side passages and function – probably an important key to still have main spongocoel their success) single osculum 1. Choanocytes (= collar cells) c. leuconoid most complex consists of many small flagellated chambers probably the most distinctive and most important no longer a central spongocoel but almost unlimited of sponge cells ability for sponge to grow in size generally larger colonial forms each mass has its own osculum each collar cell has a flagellum incurrent and excurrent canals surrounded by a sieve-like collar that acts as a a typical sponge can pump water equivalent to its own strainer volume in ~ 8 seconds “collar” is made of microvilli and microfibrils a sponge must pump >1 ton of water to get 1 oz of the flagellum beats to draw the water currents into food the sponge and then to strain particles through the collar they can also control the flow by constricting osculum at night and opening in day when food is more food is absorbed (phagocytosis) by the collar cell plentiful and then sent to other cells in the sponge also can reverse the flow to clean out canals after a choanocytes line major cavities depending on canal system: storm a. spongocoel on asconoid types b. radial canals on syconoid types like cleaning pool filters c. flagellated chambers on leuconoid types Cell Types collar cells are almost identical to the cells of choanoflagellates only a few cells have been specialized for certain Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 5 Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 6 genetic analysis indicates a very close relationship between these protists and can differentiate into any other type of cell sponges different kinds à choanoflagellates are ancestors of animals sclerocytes à secrete spicules spongocytes à secrete spongin 2. Pinacocytes collencyotes à secrete collagen form outer “epithelium” and sometimes lines Support inner passages the cells in gelatinous matrix of a sponge are arranged nearest thing to tissues around a skeleton of spicules thin flat cells spicules maintain its shape and keep pores and canals open some are contractile = myocytes in circular bands around oscula to regulate water flow spicules may be composed of: 3. Porocytes a. calcium carbonate tubular cells form the pores of asconoid sponges b. silica 4. Archaeocytes à spicules often united to form a rigid network that looks like fiberglass amoeboid type cells (eg. Venus Flower Basket) c. spongin (a form of collagen – a protein only move about in mesophyll matrix found in animals) receive particles from choanocytes for digestion à flexible protein fibers related to keratin phagocytize old cells (eg. common commercial sponge and most sponges Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 7 Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 8 normally encountered on reefs) within days other “tentacles” grow around victim and engulf Feeding and Digestion and digest it 1. all but a few sponges are filter feeders 3. a small number of sponges are “parasites” feed on detritus, plankton, bacteria = boring sponges (demospongiae) pinacocytes, archaeocytes and choanocytes can all phagocytize excavates hollow tubes and passageways into shells and food corals (living or dead host shells) or limetone rock archaeocytes can eat larger particles choanocytes can eat smaller particles the animal grows into the canals and holes it creates when boring into live animal shells the host will either die sponges can also absorb dissolved nutrients outright or be much more susceptible to predation directly from the water may have significant impacts on coral reefs and oyster reefs digestion is all intracellular important in recycling shells and corals = “bioerosion” each cell is responsible for getting its own food in some areas bridge supports are no longer constructed of limestone because it is attacked by these sponges 2. one sponge is a predator No respiratory or Excretory Systems until 90’s all sponges were thought to be filter feeding omnivores take in O2 and get rid of wastes and CO2 by simple diffusion one sponge from Mediterranean is now known to be a predator = Cladorhiza corona a few have contractile vacuoles in choanocytes and archaeocytes found in Mediterranean caves lives in stagnant water à not much to filter No Nervous System or Sense Organs has developed a tentacle like appendge covered with velcro-like hooks sponges can react to local stimuli the hooks snag shrimplike crustacea some produce electrical signals Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 9 Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 10 specialized sex cells in mesenchyme form egg sponges do produce some hormones for chemical or sperm control sperm released into water Reproduction & Development eggs are retained in mesenchyme reproduce both sexually and asexually sperm are drawn into female sponge Asexual through ostia or pores and fertilize a. regeneration egg b. asexual buds: most sponges are viviparous may break off or remain attached to form =retain and nourish embryo colonies free swimming ciliated larvae hatch and are c. fw & a few marine forms produce internal released buds = gemmules unique larval form = amphiblastula à dormant masses of encapsulated swims in plankton for a while then turns cells inside-out and settles to become a sessile adult usually produced during harsh conditions may be retained inside “parent” sponge or as original sponge dies, they fall to bottom Sexual some sponges are monoecious, some are dioecious Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 11 Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 12 Sponge Classification [not current taxonomy] Phylogeny of Sponges A. Class Calcarea (calcareous sponges) origin dates to cambrian small, vase shaped, primitive group related to flagellate protozoans mostly drab coloried; a few are yellow, red, green, lavender all marine, especially shallow waters à choanoflagellates show all 3 types of canal systems; mostly asconoid canals spicules of CaCO , needle shaped or 3-4 rayed 3 sponges diverged early new genetic analysis (2010) indicate that sponges B.
Load more

Recommended publications
  • PALEONTOLOGICAL TECHNICAL REPORT: 6Th AVENUE and WADSWORTH BOULEVARD INTERCHANGE PHASE II ENVIRONMENTAL ASSESSMENT, CITY of LAKEWOOD, JEFFERSON COUNTY, COLORADO
    PALEONTOLOGICAL TECHNICAL REPORT: 6th AVENUE AND WADSWORTH BOULEVARD INTERCHANGE PHASE II ENVIRONMENTAL ASSESSMENT, CITY OF LAKEWOOD, JEFFERSON COUNTY, COLORADO Prepared for: TEC Inc. 1746 Cole Boulevard, Suite 265 Golden, CO 80401 Prepared by: Paul C. Murphey, Ph.D. and David Daitch M.S. Rocky Mountain Paleontology 4614 Lonespur Court Oceanside, CA 92056 303-514-1095; 760-758-4019 www.rockymountainpaleontology.com Prepared under State of Colorado Paleontological Permit 2007-33 January, 2007 TABLE OF CONTENTS 1.0 SUMMARY............................................................................................................................. 3 2.0 INTRODUCTION ................................................................................................................... 4 2.1 DEFINITION AND SIGNIFICANCE OF PALEONTOLOGICAL RESOURCES........... 4 3.0 METHODS .............................................................................................................................. 6 4.0. LAWS, ORDINANCES, REGULATIONS AND STANDARDS......................................... 7 4.1. Federal................................................................................................................................. 7 4.2. State..................................................................................................................................... 8 4.3. County................................................................................................................................. 8 4.4. City.....................................................................................................................................
    [Show full text]
  • Phylum Arthropod Silvia Rondon, and Mary Corp, OSU Extension Entomologist and Agronomist, Respectively Hermiston Research and Extension Center, Hermiston, Oregon
    Phylum Arthropod Silvia Rondon, and Mary Corp, OSU Extension Entomologist and Agronomist, respectively Hermiston Research and Extension Center, Hermiston, Oregon Member of the Phyllum Arthropoda can be found in the seas, in fresh water, on land, or even flying freely; a group with amazing differences of structure, and so abundant that all the other animals taken together are less than 1/6 as many as the arthropods. Well-known members of this group are the Kingdom lobsters, crayfish and crabs; scorpions, spiders, mites, ticks, Phylum Phylum Phylum Class the centipedes and millipedes; and last, but not least, the Order most abundant of all, the insects. Family Genus The Phylum Arthropods consist of the following Species classes: arachnids, chilopods, diplopods, crustaceans and hexapods (insects). All arthropods possess: • Exoskeleton. A hard protective covering around the outside of the body (divided by sutures into plates called sclerites). An insect's exoskeleton (integument) serves as a protective covering over the body, but also as a surface for muscle attachment, a water-tight barrier against desiccation, and a sensory interface with the environment. It is a multi-layered structure with four functional regions: epicuticle (top layer), procuticle, epidermis, and basement membrane. • Segmented body • Jointed limbs and jointed mouthparts that allow extensive specialization • Bilateral symmetry, whereby a central line can divide the body Insect molting or removing its into two identical halves, left and right exoesqueleton • Ventral nerve
    [Show full text]
  • Vertebrates and Invertebrates
    Vertebrates and invertebrates The animal kingdom is divided into two groups: vertebrates and invertebrates. Vertebrates have been around for millions of years but have evolved and changed over time. The word vertebrate means “having a backbone." Many animals have backbones. You have a backbone. So does a cow, a whale, a fish, a frog, and a bird. Vertebrates are animals that have a backbone. Most animals have a backbone that is made of bones joined together to form a skeleton. Our skeleton gives us our shape and allows us to move. Mammals, fish, birds, reptiles, and amphibians have Vertebrae backbones so they are all vertebrates. Each bone that makes up the backbone Scientists classify vertebrates into five classes: is called a vertebra. These are the • Mammals building blacks that form the backbone, • Fish also known as the spinal cord. The • Birds vertebrae protect and support your • Reptiles spine. Without a backbone, you would not • Amphibians be able to move any part of your body. Animals without a backbone are called invertebrates. Most The human animals are invertebrates. In fact, 95% of all living creatures backbone has 26 on Earth are invertebrates. vertebrae. Arthropods are the largest group of invertebrates. Insects make up a large part of this group. All insects, such as ladybugs, ants, grasshoppers, and bumblebees have three body sections and six legs. Most arthropods live on land, but some of these fascinating creatures live in water. Lobsters, crabs, and shrimp are arthropods that live in the oceans. Many invertebrates have skeletons on the outside of their A frog only has bodies called exoskeletons.
    [Show full text]
  • Introduction to Phylum Chordata
    Unifying Themes 1. Chordate evolution is a history of innovations that is built upon major invertebrate traits •bilateral symmetry •cephalization •segmentation •coelom or "gut" tube 2. Chordate evolution is marked by physical and behavioral specializations • For example the forelimb of mammals has a wide range of structural variation, specialized by natural selection 3. Evolutionary innovations and specializations led to adaptive radiations - the development of a variety of forms from a single ancestral group Characteristics of the Chordates 1. Notochord 2. dorsal hollow nerve cord 3. pharyngeal gill slits 4. postanal tail 5. endostyle Characteristics of the Chordates Notochord •stiff, flexible rod, provides internal support • Remains throughout the life of most invertebrate chordates • only in the embryos of vertebrate chordates Characteristics of the Chordates cont. Dorsal Hollow Nerve Cord (Spinal Cord) •fluid-filled tube of nerve tissue, runs the length of the animal, just dorsal to the notochord • Present in chordates throughout embryonic and adult life Characteristics of the Chordates cont. Pharyngeal gill slits • Pairs of opening through the pharynx • Invertebrate chordates use them to filter food •In fishes the gill sits develop into true gills • In reptiles, birds, and mammals the gill slits are vestiges (occurring only in the embryo) Characteristics of the Chordates cont. Endostyle • mucous secreting structure found in the pharynx floor (traps small food particles) Characteristics of the Chordates cont. Postanal Tail • works with muscles (myomeres) & notochord to provide motility & stability • Aids in propulsion in nonvertebrates & fish but vestigial in later lineages SubPhylum Urochordata Ex: tunicates or sea squirts • Sessile as adults, but motile during the larval stages • Possess all 5 chordate characteristics as larvae • Settle head first on hard substrates and undergo a dramatic metamorphosis • tail, notochord, muscle segments, and nerve cord disappear SubPhylum Urochordata cont.
    [Show full text]
  • Fins, Limbs, and Tails: Outgrowths and Axial Patterning in Vertebrate Evolution Michael I
    Review articles Fins, limbs, and tails: outgrowths and axial patterning in vertebrate evolution Michael I. Coates1* and Martin J. Cohn2 Summary Current phylogenies show that paired fins and limbs are unique to jawed verte- brates and their immediate ancestry. Such fins evolved first as a single pair extending from an anterior location, and later stabilized as two pairs at pectoral and pelvic levels. Fin number, identity, and position are therefore key issues in vertebrate developmental evolution. Localization of the AP levels at which develop- mental signals initiate outgrowth from the body wall may be determined by Hox gene expression patterns along the lateral plate mesoderm. This regionalization appears to be regulated independently of that in the paraxial mesoderm and axial skeleton. When combined with current hypotheses of Hox gene phylogenetic and functional diversity, these data suggest a new model of fin/limb developmental evolution. This coordinates body wall regions of outgrowth with primitive bound- aries established in the gut, as well as the fundamental nonequivalence of pectoral and pelvic structures. BioEssays 20:371–381, 1998. ௠ 1998 John Wiley & Sons, Inc. Introduction over and again to exemplify fundamental concepts in biological Vertebrate appendages include an amazing diversity of form, theory. The striking uniformity of teleost pectoral fin skeletons from the huge wing-like fins of manta rays or the stumpy limbs of illustrated Geoffroy Saint-Hilair’s discussion of ‘‘special analo- frogfishes, to ichthyosaur paddles, the extraordinary fingers of gies,’’1 while tetrapod limbs exemplified Owen’s2 related concept aye-ayes, and the fin-like wings of penguins. The functional of ‘‘homology’’; Darwin3 then employed precisely the same ex- diversity of these appendages is similarly vast and, in addition to ample as evidence of evolutionary descent from common ances- various modes of locomotion, fins and limbs are also used for try.
    [Show full text]
  • Vertebrates in the Animal Kingdom
    Science Enhanced Scope and Sequence – Grade 5 Vertebrates in the Animal Kingdom Strand Living Systems Topic Investigating characteristics of organisms Primary SOL 5.5 The student will investigate and understand that organisms are made of one or more cells and have distinguishing characteristics that play a vital role in the organism’s ability to survive and thrive in its environment. Key concepts include b) classification of organisms using physical characteristics, body structures, and behavior of the organism; c) traits of organisms that allow them to survive in their environment. Related SOL 5.1 The student will demonstrate an understanding of scientific reasoning, logic, and the nature of science by planning and conducting investigations in which a) items such as rocks, minerals, and organisms are identified using various classification keys. Background Information To study organisms, scientists first look at their characteristics and group the organisms based on the characteristics they share. Some animals are so small that they live on or inside other animals. Others, such as the giant squid, are many meters long and live in the depths of oceans. Animals can swim, crawl, burrow, fly, or not move at all. No matter what their size, where they live, or how they move, all animals must have some basic characteristics in common. All organisms in the animal kingdom (1)) are made of cells, (2 reproduce, (3) grow and develop, (4) have a life cycle, (5) obtain and use energy, and (6) responds and adapt to their environment. In the 18th century, a Swedish scientist named Carolus Linnaeus developed a system to organize living things.
    [Show full text]
  • Evolutionary Crossroads in Developmental Biology: Cyclostomes (Lamprey and Hagfish) Sebastian M
    PRIMER SERIES PRIMER 2091 Development 139, 2091-2099 (2012) doi:10.1242/dev.074716 © 2012. Published by The Company of Biologists Ltd Evolutionary crossroads in developmental biology: cyclostomes (lamprey and hagfish) Sebastian M. Shimeld1,* and Phillip C. J. Donoghue2 Summary and is appealing because it implies a gradual assembly of vertebrate Lampreys and hagfish, which together are known as the characters, and supports the hagfish and lampreys as experimental cyclostomes or ‘agnathans’, are the only surviving lineages of models for distinct craniate and vertebrate evolutionary grades (i.e. jawless fish. They diverged early in vertebrate evolution, perceived ‘stages’ in evolution). However, only comparative before the origin of the hinged jaws that are characteristic of morphology provides support for this phylogenetic hypothesis. The gnathostome (jawed) vertebrates and before the evolution of competing hypothesis, which unites lampreys and hagfish as sister paired appendages. However, they do share numerous taxa in the clade Cyclostomata, thus equally related to characteristics with jawed vertebrates. Studies of cyclostome gnathostomes, has enjoyed unequivocal support from phylogenetic development can thus help us to understand when, and how, analyses of protein-coding sequence data (e.g. Delarbre et al., 2002; key aspects of the vertebrate body evolved. Here, we Furlong and Holland, 2002; Kuraku et al., 1999). Support for summarise the development of cyclostomes, highlighting the cyclostome theory is now overwhelming, with the recognition of key species studied and experimental methods available. We novel families of non-coding microRNAs that are shared then discuss how studies of cyclostomes have provided exclusively by hagfish and lampreys (Heimberg et al., 2010).
    [Show full text]
  • The Evolution of the Mitochondrial Genomes of Calcareous Sponges and Cnidarians Ehsan Kayal Iowa State University
    Iowa State University Capstones, Theses and Graduate Theses and Dissertations Dissertations 2012 The evolution of the mitochondrial genomes of calcareous sponges and cnidarians Ehsan Kayal Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/etd Part of the Evolution Commons, and the Molecular Biology Commons Recommended Citation Kayal, Ehsan, "The ve olution of the mitochondrial genomes of calcareous sponges and cnidarians" (2012). Graduate Theses and Dissertations. 12621. https://lib.dr.iastate.edu/etd/12621 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. The evolution of the mitochondrial genomes of calcareous sponges and cnidarians by Ehsan Kayal A dissertation submitted to the graduate faculty in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Major: Ecology and Evolutionary Biology Program of Study Committee Dennis V. Lavrov, Major Professor Anne Bronikowski John Downing Eric Henderson Stephan Q. Schneider Jeanne M. Serb Iowa State University Ames, Iowa 2012 Copyright 2012, Ehsan Kayal ii TABLE OF CONTENTS ABSTRACT ..........................................................................................................................................
    [Show full text]
  • Vertebrate Animals Rules Rules Involving Vertebrate Animals
    Vertebrate Animals Rules Rules involving vertebrate animals The following rules were developed to help pre-college student b. Description of how the animals will be used. Include researchers adhere to the federal regulations governing methods and procedures, such as experimental design professional scientists and to protect the welfare of both and data analysis; description of the procedures that will animal subjects and the student researcher. Health and well- minimize the potential for discomfort, distress, pain and being is of high priority when students conduct research with injury to the animals during the course of experimentation; animal subjects. identifi cation of the species, strain, sex, age, weight, source and number of animals proposed for use. The Society strongly endorses the use of non-animal research methods and encourages students to use alternatives to animal 2. All vertebrate animal studies must be reviewed and approved research, which must be explored and discussed in the research before experimentation begins. An Institutional Animal Care plan. The guiding principles for the use of animals in research and Use Committee, known as an IACUC, is the institutional include the following “Four R’s”: animal oversight review and approval body for all animal • Replace vertebrate animals with invertebrates, lower life studies at a Regulated Research Institution. The local OR forms, tissue/cell cultures and/or computer simulations where affi liated fair SRC serves in this capacity for vertebrate animals possible. studies performed in a school, home or fi eld. Any SRC serving • Reduce the number of animals without compromising in this capacity must include a veterinarian or an animal care statistical validity.
    [Show full text]
  • Lesson 2 Craniate/Vertebrate Characteristics Lesson Outline
    Lesson 2 Craniate/Vertebrate Characteristics ◊ Lesson Outline: ♦ Protostomes versus Deuterostomes ♦ The Chordate Body Plan ♦ Craniate Characteristics ♦ Vertebrate Characteristics ♦ Origin of the Chordates ◊ Objectives: At the end of this lesson you should be able to: ♦ Distinguish between prototomes and deuterostomes ♦ Describe the features of the basic chordate body plan ♦ Describe the characteristics common to all craniates ♦ Describe the characteristics that distinguish craniates and vertebrates ♦ Describe the origin of the Chordates ◊ References: ♦ Chapter 1 and 3 (read only) ◊ Reading for Next Lesson: ♦ Chapter 4 Chordate Body Plan Despite the tremendous diversity within the animal kingdom, there are only a few different types of body plan Large numbers of animals are descendent from common ancestors and the common ancestry determines much of the basic similarity in body organization Thus, all chordates have a common body plan that is unique to this group. Other plans include: Coelenterate Body Plan Flatworm Body Plan Round Worm Body Plan Annelid Body Plan Arthropod Body Plan Molluscan Body Plan Ecinoderm Body Plan Chordate/Vertebrate Body Plan There are departures from each plan (parasites for instance) raising questions about "Why" and "How" they have occurred. Protostomes vs Deuterostomes (not in textbook) The chordates are descended from ancestors that were distinguished by the fact that at some point in their development they were bilaterally symmetrical and had a coelom or body cavity. Within the coelomates two distinct and independent evolutionary lines are present. One line is the protostomes, which includes the molluscs, annelids, arthropods and many smaller groups. The other line is the deuterostomes which includes the echinoderms, protochordates and chordates The division into these two groups has been made based on embryonic characteristics.
    [Show full text]
  • Six Major Steps in Animal Evolution: Are We Derived Sponge Larvae?
    EVOLUTION & DEVELOPMENT 10:2, 241–257 (2008) Six major steps in animal evolution: are we derived sponge larvae? Claus Nielsen Zoological Museum (The Natural History Museum of Denmark, University of Copenhagen), Universitetsparken 15, DK-2100 Copenhagen, Denmark Correspondence (email: [email protected]) SUMMARY A review of the old and new literature on animal became sexually mature, and the adult sponge-stage was morphology/embryology and molecular studies has led me to abandoned in an extreme progenesis. This eumetazoan the following scenario for the early evolution of the metazoans. ancestor, ‘‘gastraea,’’ corresponds to Haeckel’s gastraea. The metazoan ancestor, ‘‘choanoblastaea,’’ was a pelagic Trichoplax represents this stage, but with the blastopore spread sphere consisting of choanocytes. The evolution of multicellularity out so that the endoderm has become the underside of the enabled division of labor between cells, and an ‘‘advanced creeping animal. Another lineage developed a nervous system; choanoblastaea’’ consisted of choanocytes and nonfeeding cells. this ‘‘neurogastraea’’ is the ancestor of the Neuralia. Cnidarians Polarity became established, and an adult, sessile stage have retained this organization, whereas the Triploblastica developed. Choanocytes of the upper side became arranged in (Ctenophora1Bilateria), have developed the mesoderm. The a groove with the cilia pumping water along the groove. Cells bilaterians developed bilaterality in a primitive form in the overarched the groove so that a choanocyte chamber was Acoelomorpha and in an advanced form with tubular gut and formed, establishing the body plan of an adult sponge; the pelagic long Hox cluster in the Eubilateria (Protostomia1Deuterostomia). larval stage was retained but became lecithotrophic. The It is indicated that the major evolutionary steps are the result of sponges radiated into monophyletic Silicea, Calcarea, and suites of existing genes becoming co-opted into new networks Homoscleromorpha.
    [Show full text]
  • SVP Comments on 21 U.S. National
    Society of Vertebrate Paleontology 9650 Rockville Pike Bethesda, MD 20814- 3998 Phone: (301) 634-7814 Fax: (301) 634-7455 Email: [email protected] Web: www.vertpaleo.org FEIN: 06-0906643 July 9, 2017 Subject: Comments from the Society of Vertebrate Paleontology about the scientific importance of paleontological resources at the 21 U.S. National Monuments established since 1996 (Docket ID: DOI-2017-0002). Executive Summary In this document, the Society of Vertebrate Paleontology reviews the paleontological resources currently known from the U.S. National Monuments established since 1996 and explains why altering or revoking their boundaries would be disastrous for the science of paleontology. In these comments, we present: i. our views on the role of public lands in the science of paleontology (p. 2); ii. information on the benefit of paleontological science and education at these monuments to the general public (p. 4); iii. comments on why mining operations are incompatible with discovery and scientific study of paleontological resources (p. 4); iv. specific details about the paleontological resources at each of the continental monuments under review (p 6); v. a copy of the comments we submitted on May 25, 2017, about Bears Ears and Grand Staircase-Escalante National Monuments (tracking number 1k1-8wld-cxoj) (Appendix 1, p. 17); vi. representative scientific publications on paleontological resources at each of the moments (Appendix 2, p. 25) We find that all 21 non-marine monuments protect scientifically important vertebrate fossils or rocks with a high potential for yielding them, and are therefore are appropriately designated under the Antiquities Act of 1906 (note: ‘fossils’ must not to be confused with ‘fossil fuels’).
    [Show full text]